Not Applicable
1. Field of the Invention
This invention relates to medical device delivery catheters in general, and specifically to balloon catheters for use in delivering a medical device such as a stent to a desired body location, such as in a blood vessel. More specifically, this invention relates to a stent retaining sock or sleeve composed of a matrix of generally elastic material which also includes at least one substantially longitudinally oriented fiber or filament which is harder than the surrounding elastic material and imbedded therein. The filaments may be a singular fiber or be comprised of a braid of several fibers woven together. The combination of the elastomeric sleeve material and reinforcing fiber(s) (braids) provide for a sleeve, which when mounted on a stent delivery balloon catheter, may be expanded in the radial direction during balloon expansion, but which may longitudinally foreshorten during the expansion, thereby causing the ends of the sleeve to retract off of the ends of the stent in a safe and efficient manner.
2. Description of the Related Art
Stents and stent delivery assemblies are utilized in a number of medical procedures and situations, and as such their structure and function are well known. A stent is a generally cylindrical prosthesis introduced via a catheter into a lumen of a body vessel in a configuration having a generally reduced diameter and then expanded to the diameter of the vessel. In its expanded configuration, the stent supports and reinforces the vessel walls while maintaining the vessel in an open, unobstructed condition.
Both self-expanding and inflation expandable stents are well known and widely available in a variety of designs and configurations. Self-expanding stents must be maintained under positive external pressure in order to maintain their reduced diameter configuration during delivery of the stent to its deployment site. Inflation expandable stents may be crimped to their reduced diameter about the delivery catheter, maneuvered to the deployment site, and expanded to the vessel diameter by fluid inflation of a balloon positioned on the delivery catheter. The present invention is particularly concerned with delivery and deployment of inflation expandable stents, although it is generally applicable to self-expanding stents when used with balloon catheters.
In advancing an inflation expandable stent through a body vessel to the deployment site, there are a number of important considerations. The stent must be able to securely maintain its axial position on the delivery catheter, without translocating proximally or distally, and especially without becoming separated from the catheter. The stent, particularly its distal and proximal ends, must be protected to prevent distortion of the stent and to prevent abrasion and/or reduce trauma of the vessel walls.
Inflation expandable stent delivery and deployment assemblies are known which utilize restraining means that overlie the stent during delivery. U.S. Pat. No. 4,950,227 to Savin et al, relates to an expandable stent delivery system in which a sleeve overlaps the distal or proximal margin (or both) of the stent during delivery. That patent discloses a stent delivery system in which a catheter carries, on its distal end portion, a stent which is held in place around the catheter prior to and during percutaneous delivery by means of one and preferably two sleeves. The sleeves are positioned around the catheter with one end portion attached thereto and overlap an end portion(s) of the stent to hold it in place on the catheter in a contracted condition. Each sleeve is elastomeric in nature so as to stretch and release the stent when it expands for implantation. The stent is expandable by means of the expandable balloon on the catheter. During expansion of the stent at the deployment site, the stent margins are freed of the protective sleeve(s). U.S. Pat. No. 5,403,341 to Solar, relates to a stent delivery and deployment assembly which uses retaining sheaths positioned about opposite ends of the compressed stent. The retaining sheaths of Solar are adapted to tear under pressure as the stent is radially expanded, thus releasing the stent from engagement with the sheaths. U.S. Pat. No. 5,108,416 to Ryan et al., describes a stent introducer system which uses one or two flexible end caps and an annular socket surrounding the balloon to position the stent during introduction to the deployment site.
Copending U.S. patent application Ser. No. 09/426,384 which was filed Oct. 26, 1999 and entitled Longitudinal Dimensional Stable Balloons, and which is incorporated in its entirety herein by reference describes balloon material having longitudinally oriented fibers.
Copending U.S. patent application Ser. No. 09/407,836 which was filed on Sep. 28, 1999 and entitled Stent Securement Sleeves and Optional Coatings and Methods of Use, and which is incorporated in its entirety herein by reference, provides for a stent delivery system having sleeves. In U.S. Ser. No. 09/407,836 the sleeves may be made up of a combination of polytetrafluoroethylene (PTFE) as well as one or more thermoplastic elastomers. Other references exist which disclose a variety of stent retaining sleeves.
In many prior stent delivery systems which utilize retractable sleeves to retain the ends of the stent to the catheter prior to delivery, such as those described above, the expansion characteristics of the sleeves are such that typically the sleeves will foreshorten by less than 5 percent as a result of balloon expansion. This nominal foreshortening may assist in retracting the sleeves off of the stent ends but other attributes such as reduced frictional interface between the sleeve and stent and/or reduced columnar strength of the sleeve may also be required to effectively retract the sleeves from the stent.
As indicated above, a common problem which occurs in catheter assemblies is friction or adhesion between various parts which periodically come into contact with one another during the medical procedure. For instance, friction can occur between the guide catheter and guide wire, between the introducer sheath and the guide catheter, or between the guide catheter and the balloon catheter, for instance, and may increase the difficulty of insertion, cause loss of catheter placement, and result in discomfort to the patient or damage to the vasculature. In catheters equipped with stent retaining socks or sleeves, friction between the balloon and sleeve, and/or the stent and sleeve may also cause retraction of the sleeves to be made more difficult. It is therefore desirable to reduce the friction due to the sliding between the various parts of the catheter assemblies, most notably between the ends of the stent and the portions of the sleeves which retain the ends to the catheter prior to stent implantation.
Copending U.S. application Ser. No. 09/549,286 which was filed Apr. 14, 2000 describes a reduced columnar strength stent retaining sleeve having a plurality of holes. The relatively reduced columnar and radial strength provided by the holes allows the sleeve to be retracted off of a stent without the need for lubricant. However, lubricants may be used to further assist in sleeve retraction.
Lubricants of many types have been used in conjunction with balloon catheters. Both hydrophilic and hydrophobic coatings and lubricants are well known in the catheter art. The present invention may be used in conjunction with any type of lubricious substance suitable for use with a stent delivery catheter, and is further directed to the application of the lubricious substance to the surface of a balloon cone and/or waste subsequent to stent mounting and sleeve placement onto the catheter.
Copending U.S. patent application Ser. No. 09/427,805 filed Oct. 27, 1999, and entitled End Sleeve Coating for Stent Delivery, describes the use of stent retaining sleeves having lubricious coatings applied thereto. Copending U.S. patent application Ser. No. 09/273,520 filed Mar. 22, 1999, entitled Lubricated Sleeve Material For Stent Delivery likewise describes the use of stent retaining sleeves and lubricants.
The entire content of all patents and applications listed within the present patent application are incorporated herein by reference.
While the various concepts mentioned above as well as those described in the various references cited herein may provide a variety of means for improving sleeve retraction from a stent during balloon expansion, it remains desirable to further improve upon retractable sleeves and stent delivery systems in general. The present invention is directed to a sleeve and/or an associated stent delivery system wherein the sleeve may be readily retracted from a stent as a result of longitudinal foreshortening of the sleeve which occurs during radial expansion.
As indicated above the present invention is directed to a retractable stent retaining sleeve, or pair of sleeves, which may be disposed about the respective ends of a stent to retain the ends of the stent on a stent mounting region of a balloon catheter. The sleeve are retracted off of the stent during the stent delivery process when a balloon or an inflatable portion of the catheter is inflated to radially expand the stent. As the stent is subjected to radial expansion so to is at least a portion of the stent retaining sleeve. The unique construction of the present sleeve provides the sleeves with the capacity to be retracted off of the ends of a stent during balloon expansion to release the stent.
In at least one embodiment of the invention the sleeves are constructed and arranged to foreshorten to an extent greater than previous stent retaining sleeves or socks, thereby providing for improved retraction from the stent ends.
In at least one embodiment of the invention, the length of the sleeves is foreshortened more than 5 percent during sleeve retraction.
In at least one embodiment of the invention, the length of the sleeves is foreshortened 20 percent or more during sleeve retraction.
In at least one embodiment, the instant invention is directed to a medical device delivery system comprising a catheter assembly having a medical device receiving region and at least one retaining sleeve for retaining the medical device on the receiving region prior to delivery. An expandable medical device, such as a stent, is disposed about the medical device receiving region of the catheter assembly. At least one retaining sleeve is disposed about an end of the expandable medical device and at least a portion of the catheter assembly.
In at least one embodiment of the invention, the retractable stent retaining sleeve comprises a first material and a second material, wherein the second material is harder than the first material. The second material may be one or more fibers or braids of fiber of a predetermined material or combination of materials. The fibers may be oriented relative to the longitudinal axis of the retaining sleeve in a variety of patterns. For example the fibers may be substantially parallel to the longitudinal axis of the sleeve, angled relative thereto, helically or otherwise disposed thereabout, etc.
In at least one embodiment of the invention, the fiber(s) or stripe(s) may be disposed about the inside and/or outside of the sleeve.
In yet another embodiment of the invention, the stripes of a second material may be fully enclosed, or xe2x80x9csandwichedxe2x80x9d within the matrix of the first material. It should be noted that while the second material may be characterized as being harder than the first material, the second material have additional or alternative features which are different that the first. For example, the first and second material may have different: flexibility, elasticity, tensile modulus, modulus of elasticity, as well as many other characteristics which may be different from one another.
In still another embodiment of the invention the matrix of the sleeve, i.e. the first material, may itself be comprised of a variety of materials, such that the stripe(s) may be enclosed between an inside layer of material and an outside layer of material wherein the inside material and the outside material are different from one another.